Buffer PH level up every two days!

Our PH levels dropped from well water of 8.2 over time to 6.4. I am now constantly buffering the water up to 6.8. When it drops to 6.4 I buffer it up to 6.8. The problem is that this process happens every 2 days and it is a pain. I need something that will help keep the level more consistent over a week or two if this is reasonable, Input would be great....